Update for 6/30/10: Two microarray platforms (our Agilent chip containing disease resistant genes and the Affymetrix Citrus GeneChip) are being used to compare gene expression over time in response to canker and HLB. Comparisons are being made between resistant kumquat and susceptible grapefruit for canker, and HLB tolerant rough lemon and susceptible sweet oranges are being compared. Comparisons of carbohydrate metabolism in HLB-infected and healthy plants revealed that starch, sucrose, and glucose accumulated in infected leaves, maltose decreased and fructose levels were unchanged. Comparisons of cell-wall bound invertase, a critical enzyme involved in sucrose metabolism and plant defenses, have shown its activity to be induced 4-fold in both symptomatic and asymptomatic leaves of infected sweet orange. Further, the expression profiles of 2 starch breakdown genes are downregulated. Transgenic studies are proceeding, with several hundred plants containing various new combinations of natural or synthetic genes and promoters produced; these are currently being propagated for field trials or are already in greenhouse testing. New candidate genes have been identified from citrus and other plants for HLB and canker resistance, from gene expression studies and data mining of public EST databases; vectors are being produced for a next round of transgenic plant production. Phloem-specific promoters are being identified for incorporation in constructs to produce more consumer friendly transgenic plants, by limiting transgene expression to specific tissues. Previously, microarray experiments highlighted canker defensive genes in kumquat; real-time PCR confirmed their roles, and these will be used in new transformation experiments to produce canker resistant citrus. Cybrid grapefruit plants showing tolerance to canker in greenhouse tests have been planted in the Indian River area to assess field tolerance to canker. New DNA samples from a genetic population are being genotyped with previously developed SSR markers to develop a high density genetic linkage map to aid genome sequence assembly and validation; this is part of the international genome sequencing collaboration. Several new rootstock trials with more than 15,000 trees have been or will be planted throughout Florida using advanced selections, to assess their adaptation to evolving advanced citrus production systems; these trials are monitored regularly. Rootstock candidates that produce nucellar seedlings are being identified routinely using SSR markers; these rootstocks were preselected for potential tree size control and some for tolerance of Diaprepes/Phytophthora. Four complex tetraploid rootstocks are showing some suppression of HLB symptoms in greenhouse tests that are still underway. New crosses for rootstock improvement were made in 2010, using previously proven parental lines. New pummelo-grapefruit seedless hybrids selected the past 2-3 years, as well as breeding parents, are being assayed for fruit furanocoumarin content; several have been found FC-free. Genetic studies are underway using in silico expression approaches to EST data analysis to define the genetic controlling elements of this trait, which seems to be simply inherited based on preliminary results.